Y-Site Compatibility of Vancomycin and Piperacillin/ Tazobactam at Commonly Utilized Pediatric Concentrations

Background: Vancomycin and piperacillin/tazobactam are common empiric antibiotics in hospitalized pediatric patients. Studies evaluating intravenous (IV) compatibility at various concentrations show inconsistent results. Objective: The objective of this study was to determine the Y-site compatibility of vancomycin 10 mg/mL and piperacillin/tazobactam 112.5 mg/mL. Methods: Vancomycin (10 g vial) was reconstituted using sterile water for injection (SWFI) and diluted with 5% dextrose in water (D5W) to a final concentration of 10 mg/mL in an evacuated IV bag. Piperacillin/tazobactam (40.5 g vial) was reconstituted and diluted with SWFI to a final concentration of 112.5 mg/mL (100 mg/mL piperacillin) in an evacuated IV bag. Both antibacterial stock solutions were then stored in a refrigerator at 4°C (39.2°F). Initial solution appearances, including color, clarity, and particulates, were documented. Diluted solutions were mixed in a quantity of 3 mL of each vancomycin and piperacillin/tazobactam in glass test tubes. Subsequent evaluation included pH assessment and visual evaluation with unaided eye, magnifying glass, high-beam light, and via Spec-20 turbidimeter. Solution mixtures were evaluated upon mixing and again at 30 minutes, 1 hour, and 4 hours after mixing. Results: Initial combination of vancomycin and piperacillin/tazobactam resulted in a milky precipitate, visible to the unaided eye, which dissipated 15 seconds after mixing. No precipitate was visualized via any method at any additional time point. Turbidimetry and pH readings did not demonstrate differences from baseline measurements. Conclusions: A combination of vancomycin 10 mg/mL and piperacillin/tazobactam 112.5 mg/mL demonstrated precipitation immediately upon mixing. Co-infusion of vancomycin and piperacillin/tazobactam via Y-site should be considered incompatible.